Power amplifier

Abstract

A power amplifier capable of compensating for distortion by pre-distortion and achieving a large distortion suppressing effect even if IM3L components and IM3U components occurring at the power amplifier have a large level difference. A power amplifying circuit 117 amplifies an original signal. An envelope detector 119 generates an envelope signal having components identical to envelope components included in the original signal. Based on the original signal a distortion signal generating circuit 112 generates a distortion signal for canceling distortion components occurring while the original signal is amplified by the power amplifying circuit 117 . In a power combiner 116 , the envelope signal is injected to the original signal, thereby eliminating the asymmetric characteristic of the distortion components. In the power amplifying circuit 117 , the distortion signal is injected to the original signal, thereby suppressing the distortion components.

1. A power amplifier for amplifying an original signal including a plurality of signals of different frequencies, the power amplifier comprising:
 a signal input section for inputting the original signal; 
 a signal output section for outputting a signal to outside the power amplifier, wherein a route from the signal input section to the signal output section is a signal amplifying route; 
 an amplifying section for amplifying signal on the signal amplifying route; 
 an envelope signal generating section for generating an envelope signal having components identical to envelope components included in the original signal; 
 a distortion signal generating section for generating, based on the original signal, a distortion signal for canceling distortion components occurring while the signal is amplified by the amplifying section; 
 a distortion signal injecting section for injecting the distortion signal to the signal amplifying route so as to suppress the distortion components; and 
 an envelope signal injecting section for injecting the envelope signal to a distortion signal generating route from the signal input section to the distortion signal injecting section so that an asymmetric characteristic of frequency components included in the distortion signal which correspond to the distortion components coincides with an asymmetric characteristic of the distortion components. 
 
   
   
     2. The power amplifier according to  claim 1 , further comprising:
 an envelope signal detecting section for detecting a level of the envelope signal; and 
 a second envelope signal adjusting section for adjusting, based on the level of the envelope signal detected by the envelope signal detecting section, an amplitude and a phase of the envelope signal to be injected to the distortion signal generating route. 
 
   
   
     3. The power amplifier according to  claim 2 , wherein
 the second envelope signal adjusting section stores in advance a table indicative of a correspondence between a possible level of the envelope signal to be detected by the envelope signal detecting section, and an amplitude and a phase of the envelope signal when a level difference between low frequency components and high frequency components included in the distortion signal is minimum, and adjusts the amplitude and the phase of the envelope signal by using the table. 
 
   
   
     4. The power amplifier according to  claim 2 , further comprising:
 an output signal detecting section for detecting a level of an output signal from the amplifying section after injection of the envelope signal and the distortion signal; and 
 a distortion signal adjusting section for adjusting the distortion signal based on the level of the output signal detected by the output signal detecting section so that distortion components included in the output signal are at a minimum. 
 
   
   
     5. The power amplifier according to  claim 1 , wherein
 the envelope signal generating section generates the envelope signal from the original signal. 
 
   
   
     6. The power amplifier according to  claim 1 , further comprising
 a modulating section for generating a modulated signal by using a baseband signal, wherein 
 the signal input section inputs the modulated signal as the original signal, and 
 the envelope signal generating section generates the envelope signal from the baseband signal. 
 
   
   
     7. A method of amplifying an original signal including a plurality of signals of different frequencies, the method comprising:
 amplifying a signal on a signal amplifying route from an input end which inputs the original signal to an output end which outputs a signal to outside; 
 generating, based on the original signal, an envelope signal having components identical to envelope components included in the original signal; 
 generating, based on the original signal, a distortion signal for canceling distortion components occurring while the signal is amplified; 
 injecting the distortion signal to the signal amplifying route so as to suppress the distortion components; and 
 injecting the envelope signal to a distortion signal generating route from input end which inputs the original signal to an end to which the distortion signal is injected so that an asymmetric characteristic of frequency components included in the distortion signal which correspond to the distortion components coincides with an asymmetric characteristic of the distortion components.